DEOXYPENTOSE NUCLEOPROTEINS 41 



ation of their prosthetic groups, the deoxypentose nucleic acids. 

 It will not be possible to do more than mention some of the cur- 

 rent problems. For a fuller account, compare a previous survey^. 

 Reviews of the chemistry of the pentose nucleoproteins have 

 recently been published^- ^. 



2. DEOXYPENTOSE NUCLEOPROTEINS 



a. Classification 



The deoxynucleoproteins are usually defined as conjugated pro- 

 teins in which the deoxypentose nucleic acid, functioning as 

 a prosthetic group, is linked to the protein by electrostatic at- 

 traction or by secondary valence forces. It is, however, extremely 

 difficult to distinguish, in macromolecules, between these two 

 types of combination. It is, in addition, equally difficult to decide 

 whether the nucleoprotein isolated in a given case really pre- 

 existed in the cell or whether it was the result of a fortuitous 

 combination of solutes present in the same extract. A genuine 

 nucleoprotein, which in some of its properties ought to differ 

 from a mere mixture of its components, must be regarded as a 

 geometrically unique combination of two giant polyampholytes. 

 It is only recently that attempts have been made to define more 

 sharply the distinction between a nucleoprotein and a protein 

 nucleate artifact^. 



Since the deoxypentose nucleic acid fraction of a given nucleus 

 is composed of a large number of differently constituted individu- 

 als^"'^, a nucleoprotamine or a nucleohistone must comprise many 

 different conjugated proteins. A search of the literature will lead 

 to the conclusion that the number of genuine deoxypentose 

 nucleoproteins isolated until now is small. It can, moreover, not 

 yet be stated whether the major part, or all, of the deoxypentose 

 nucleic acids present in the cell occurs in the form of nucleo- 

 proteins. 



As regards the protein moiety, three principal groups of deoxy- 

 nucleoproteins may be distinguished: (1) the nucleoprotamines 

 occurring in ripe spermatozoa of many fish genera; (2) the 



References p. 60 



